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Tulip, a hooded rat, loved to play. Given the run of the house, she would scurry over to young Jaak Panksepp to play as soon as he came home from school. Today Panksepp is a neuroscientist who studies animal emotions and welfare at Washington State University in Pullman, WA. He's made a surprising discovery.
Rats chirp when they play or look forward to playing. The chirps are too high-pitched for humans to hear. Panksepp heard the rats' sounds with equipment that detects and records the presence of bats, which also make high-pitched sounds.
After playing back the tapes, he wondered, "What if this stuff is laughter?" He tickled some rats with his hand. The bat detector went crazy. The rats were laughing! While he can't prove rats have a sense of humor, he says, "For rats, laughter is the way they express joy."
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